1. Field of the Invention
This invention relates generally to valves for storage tanks, and more particularly, to a high flow emergency valve positioned substantially within the interior of a storage tank which provides a simple, sturdy structure to open and close the valve, normally maintains the valve in a closed position even in an emergency, does not impede material flow to provide high flow of material into or out of the storage tank, can be adjusted and readily can be activated from the exterior of the storage tank either manually or with additional mechanical or electrical control mechanisms.
2. Description of the Related Art
Emergency valves for storage tanks are known. An example of such a valve is illustrated in U.S. Pat. No. 4,934,403 which discloses a readily inspectable and cleanable emergency valve for a storage tank. The valve assembly is opened by a first operating unit having a portion adapted for accessibility from the exterior of the tan including a fluid power connection for selectively supplying pressurized fluid to the first operating unit. The first operating unit includes a stem 28 which bears directly on a valve head 24 connected thereto and spring loaded from the interior of the tank. Such a valve, however, cannot be activated manually and relies upon pushing open of the valve head 24 which requires further structural connections with respect to, and on the interior of, the tank to provide the necessary restrictive force against which the spring and stem can react. The additional structural connections significantly impede the flow of material into and out of the valve thereby reducing the valve flow rate.
U.S. Pat. No. 4,009,862 discloses a remotely controlled fluid pressure actuated internal emergency valve for the outlet opening of a liquid storage tank which automatically closes the outlet port in the valve in the event of various emergency situations. The valve includes a movable housing which is spring biased to maintain the housing in the closed position and is activated by hydraulic fluid controlled and provided from the exterior of the tank and valve. Such a valve, however, not only requires complex hydraulic fluid seals within the valve but cannot be activated manually and includes large structural elements positioned within the tank interior which significantly impedes the flow of material through the valve thereby reducing the valve flow rate.
It therefore would be desirable to provide an emergency valve substantially positioned within the interior of a storage tank having a high flow rate which provides a simple sturdy structure to open and close the valve, normally maintains the valve in the closed position even in an emergency, provides high material flow through the valve by reducing the valve structure which typically impedes the material flow, can be adjusted and readily can be activated from the exterior of the tank either manually or with additional mechanical or electrical control mechanisms.